The manufacture of semiconductor devices is a time consuming process that requires high levels of cleanliness throughout the many phases of the manufacturing process. Many steps of manufacturing are conducted in various classes of "clean rooms" having purified air flows to reduce the incidence of airborne particle contaminants to prescribed levels.
Clean rooms are typically designated in accordance with the number of permitted contaminants of a prescribed size per cubic foot of airspace. For example, much semiconductor manufacturing is presently conducted in Class 10 clean rooms, which have filtered air flows to permit no more than ten particles per cubic foot of up to 0.5 .mu. in size. Nevertheless, wafers upon which the semiconductor devices are assembled can become contaminated, and therefore rendered defective, by contaminants that are introduced at various process steps. For example, contamination can arise from incomplete cleansing of reagents from the wafer handling apparatus, and the like.
The presence of contaminants can have a catastrophic impact on product yield, notwithstanding an otherwise proper and complete formation of the semiconductor device. Moreover, although the wafers themselves can be properly cleansed of reagents and the like that are used incident to various manufacturing steps, the wafer handling equipment, for a variety of reasons, may not be completely cleansed of the reagents and may therefore serve as a source of wafer contamination for subsequent batches of wafers.